The isotropic regularized RKD was discussed in detail in [1]}. For the convenience of the reader, we repeat it here. The RKD is given by :

f(v) = n0(3) \(\frac{3}{2}\) 3 U(\(\frac{3}{2}\) ,\(\frac{3}{2}\) -,2)
(1+v22)--1
e-2v22

where \(v\)  is the speed, \(\Theta \)  a normalisation speed, \(n_{0}\)  the
number density, \(\kappa >0\)  a
real number, and \(\frac{\Theta }{c}<\xi <1\)  a cutoff parameter, and \(U(a,b,z)\)  is the Kummer-U function [2]}
The pressure is trace of the second order moment tensor, which for the isotrpic RKD yields: 
P = P11
